Our interdisciplinary group has developed a sac-type, air-driven paracorporeal ventricular assist pump for use in patients with profound, reversible ventricular failure after open heart operations or after myocardial infarction and shock. The pump has been used in 13 patients from 3 to 8 days during the 3 years. Six of these patients were discharged from the hospital. Five are alive and well. We propose to continue to employ this bypass pump in selected patients to determine the role of this form of therapy. Studies will be performed to evaluate the recovery of myocardial function and to determine the effect of bypass pumping on organ function. Important clinical problems exist which have limited the application and results of ventricular bypass pumping. Animal studies that are proposed to seek solutions to these problems include left ventricular bypass for myocardial infarction and shock, right ventricular support in acute right ventricular failure, and development and evaluation of optimal techniques for biventricular circulatory assistance. Certain patients with irreversible, end-stage left ventricular failure will require a "permanent" implantable left ventricular assist pump. The motor-driven, implantable assist pump being developed by our group has now been employed in 5 calves with the longest period of continuous pumping of 4 months. The two most recent implanted pumps have each been coupled to an implantable compliance chamber. We propose to continue the development of the implantable left ventricular assist pump having an initial 2 year functional life. Detailed engineering analysis will be performed to evaluate system performance and control mechanisms. Mathematical modeling of the motor, pump, and circulation will be continued. Flow studies will be performed using both cine and pulsed Doppler ultrasound techniques. The motor-driven left ventricular assist pump will be implanted in normal animals, in animals with the mitral valve occluded, and those with profound left ventricular failure. We will study the physiologic effects of assist pumping, the host-prosthetic pump interaction, and the system reliability. Our goal of this phase of the assist pump program is to complete the engineering and physiologic testing to be ready for initial patient use at the completion of the proposed grant period.